Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$154.40	11.108%	$171.5508	$171.55	$171.55	$171.60
Purchase #2	$111.33	3.271%	$114.9716	$114.97	$114.95	$115.00
Purchase #3	$83.62	3.123%	$86.2315	$86.23	$86.25	$86.20
Purchase #4	$209.88	5.830%	$222.116	$222.12	$222.10	$222.10
Purchase #5	$125.39	4.662%	$131.2357	$131.24	$131.25	$131.20
Purchase #6	$151.72	9.135%	$165.5796	$165.58	$165.60	$165.60
Purchase #7	$211.30	4.424%	$220.6479	$220.65	$220.65	$220.60
7 purchase totals =	$1,047.64		$1,112.3331	$1,112.34	$1,112.35	$1,112.30